Radio receiving system



C. V. LOGVVOOD Dec. 28, 1926.

RADIO RECEIVINE SYSTEM Filed March 10, 1921 2 Sheets-Sheet l c. v. Locawooni RADIO RCEIV'lNG SYSTEM Deb. Z8 i926.

Filed March lO, 1921 2 Sheets-Sheet 2 5 A d rflk.. d, all. f U 6W do,

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lWMNESsfaS: INVENTOR L/osm/oo dig da. y BY- l u r A TTORNE YS Jifi Patented Dec. 28, 1926.

UNITED STATES ACHARLES 'V'. LOGWOOD, OF SAN 1lR.A1\T(3IS('JO, CALIFORNIA.

RADIO RECEIVING SYSTEM.

Application filed March 10, 1921. Serial No. 451,217.

tion maybe established, or a greater distance of transmission becomes possible.

A further object ofthe invention is to provide a radio receiving system for receiving signals from'continuous wave transmitting stations, without resorting to the reduction of beats in the receiving circuit.' ne Widely used system of radio reception, known as the heterodyne system, involves the use of beats produced by establishing an oscillating circuit having a frequency slightly different from the frequency of the received signals,`

so that incoming signals produce beats which are heard in the telephones. In accordance withmy invention, oscillations in the receiving circuit are established only when the signal is coming in and these oscillations are amplified and the circuit of the amplified oscillations interrupted to produce the sounds in the telephones. The frequency of interruption is within the range of audibility, so that when signals are coming in, a note is heard in the telephones, but when no signals are coming in, there is no appreciable sound in the telephones.

Generally considered, the system of my invention comprises a thermo-ionic vacuum `tube. having interlinked grid and plate circuits, which oscillate only upon the receipt of a signal and which are provided With means for changing them rapidly from oscillating circuits to non-oscillating circuits during the receipt of a signal, `whereby the loudness and definition of the sounds in the receiver are greatly increased. The invention further contemplates further coupling of the grid and plate circuits whereby variations in the current in the plate circuit caused by variations in the grid circuits are employed to further amplify the ,variations .in the grid circuit, thus further amplifying the variations in the plate circuit.

The plate circuit isinductively the grid circuit, and constitutes a feed back circuit, in which the oscillations are of the same frequency and in phase with the oscillations in the grid circuit, thereby amplifying the oscillations in the grid circuit. Thus, during the brief interval of time rthat the grid circuit is closed, incoming oscillations causing oscillations of considerable amplitude are built up in the grid circuit and in the plate circuit and these oscillations cease abruptly when the grid circuit is opened by the interrupter. v

An incoming signal from a continuous Wave source causes a change in grid potential, causing a corresponding change of potential in the rplate circuit, which change of potential is instantaneously fed back into the grid, in the same phase and frequency as the incoming signal. The coupling between the grid circuit and plate circuit` is such that a self-oscillating grid circuit is not produced nd so that the energy in the circuit diminishes instantly on the stopping of the signal.

The invention possesses other advantageous features, some of which, with the foregoing, will be set forth at length in the followingidescr-iption Where I shall outline in full, those several forms of receiving systems, embodying my invention, which I have `selected for illustration in the drawings accompanying and forming part of the'present specification. In said drawings Ihave shown the invention..embodicdin several different circuits, but it is to be understood that I do not limit myself to the embodiment shown in said drawings, since the invention, as setforth in the claims, may be embodied in a plurality of other forms. l

Referring to said drawings:

Figure l is a diagrammatic representation of a receiving-circuit embodying my inn vention. i

Fig. 2 represents a like arrangement with the exception that the grid leak is shunted. around the condenser in the grid circuit.

Fig. 3 represents a modified form of circuit in which the controlling inductance in the grid circuit is coupled` to the transformersecondary. ,l

Fig. 4 represents a modified form of' circuit in which the coupling between the id circuit and the feed back circuit is continuously varied.

coupled to Fig. 5 represents a modified form of 110 cuit in which the electrical time constants of the grid circuit are continuously varied by a revolving condenser;

Fig. 0 represents a modified form otl circuit in which the 'feed back circuit is supplanted by an amplilier.

I have obtained loud and distinct signals with the circuit shown in Fig. 1 and 'shall describe such circuit in detail. In receiving signals from a given distant station, the signals produced in the telephones in my circuit are many times louder and more distinct than are produced in the telephones iii other well knon'n receiving `systems which are non' widely used. In experimentation, I have received the signals from a given distant station with my circuit and with the Arn'istrong circuit and in instances where the signals in the Armstrong circuit were barely perceptible, the signals produced in the telephones in my circuit could be distinctly heard many feet away. Y A

The receiving System shown in Fig. 1 comprises the grounded antenna circuit 2 containing the primary 3 of an oscillatioin transformer, the secondary 4 ot which is connected as usual in the grid circuit, which circuit also contains the shunted variable capacity 5. Arrangcdiii the circuit adja-v cent the grid 6 is a variable capacity 7. The other side of the grid-circuit is connected to the filament 8 which is adapted to be heated by current from the battery 9, and a gridA leak comprising the inductance 12 and the resistance 13 connects thel grid with the otherI side vot the circuit.

Arranged in thel grid circuit, yonl that side ot the secondary 4 remote from the grid 6, is a controlling variable inductance 14, sliunted by a variable capacity 15 and-by a a circuit containing an interrupter 16 adaptled to be driven :at a speed sutliciently high to interrupt the circuit at a high frequency, within the range of audibility.v Connected to and linked` with the'igrid circuit, is thea plate circuit, connected at one end tothe plate 17 and at the other cud .of the filament S and containing thev battery 1S, telephone receiver 10, shuntiiigcondenser 21 and inductance-QQ-Which is coupled to the primary 3 or secondary 4 of the oscillation transformer. This coupling should be sufficiently tight to cause the energy in the grid circuit to build 'up during the period of oscillation ot'y the grid circuit` but not suticiently tight toinake the grid circuit a continuously o'stained excellent results when the circuit is tuned to 13,000 meters with the following cillating circuit. f

The impedance ol" the inductance 14 and the condenser 15, or the impedance ofthe' inducta'nce 14 alone (the use of the condenser lrnot being essential) is so'cliosen withrelatfion tothe values ofthe inductance 4 and the condenser 5, that the grid-circuit does noty oscillate when no signals are being' received' and when signals are receivedgfdoes `uct/os- 'iiiductance 4, 240 millilienrys; inductance igeiaisfi cillate when the interru ter 16 is open. This impedance value should preferably be high in orderto stop the grid current 110W when the interrupter is open, and with this condition existing no sound due to lthe interrupter is heard in the telephones. The signal intensity of the telephones is greatest when the value 'of the. impedance is just suicient to stop the sound of the interrupter in the ltelephones.

T he system is not in oscillation until some external torce, such as a received signal, acts on it, so that with the intcrrupter in operation and no signal being received, no sound. is produced in the telephones. The received signal current acting in the circuit ofthe inductaiico 4, condenser 5, Supplies sufficient electromotive :torce to cause the system to oscillate during the time tliattl'ie interruptei' is closed and the signal is produced in the telephones as the result of the plate circuit current changes that follow the change from a noii-oscillating to an oscillating condition,r

and vice versa. The received signal current changes the circuit, when the iiiterrupter is closed, from a iion-oscillatin 'condition to an oscillating condition and idylle opening ot' the interrupter changes it back to a non oscillating condition; During the condition of oscillation, ,the oscillations produced in the plate circuit are efectiv'e,`due to the coupling of the plate circuit 'with the grid circuit, to build up or amplify the energydn the grid circuit lWith the resultant amplication of the plate circuit current variations. Upon lthe opening of the interrupter, the condition of oscillation immediately land abruptly ceases. rlhere is, therefore, produced, during the receipt, for instance, of a Wave-train representing adasli, a seriesof amplifications ofgrid circuit current with intervening abru t collapses, producing loud and de'finitesignals in the telephones. Y Y,

The more'nearly the impedance value of the element or elements short ciicuited by the interrupter is brought to the critical point J 9 c l where it is just sutlicient to prevent oscillations when the interi'upter is momentarily opened,"the inore easily do the incoming oscillations cause the system to oscillate and the signals are much stronger since the nnpedance permits the optimum grid current to flou', when the said grid current is not suiicient to cause oscillations in the system in the absence of the received signal current.

In thesystem shown in Fig. 1, I have obvalues 'ot the constants in the circuit to wit- 22 4240 millihenrys; inductance 14, 1 henry; in lductaiice 12, .8 henry; capacity 5, .0003 mf.; capacity 7, .0002 mf.; capacity 15, .0001 mf.; capacity 21, .006 mt.; resistancel 13, 54,000 ohms; battery 18 of 40 volts. I do not de results.

sire it to be understood that 13,000 meters is the only wave length that this circuit Will effectively receive, since with these same values, signals of from 10,000 meters to 25,000 meters are readily received. In comparing signal strength between this system and heterodyne reception,"using a standard andI audibility meter, the ratio is about 1,000 to 1, that is, signals having an audibility value of 10 by the heterodyne systemhave an audibility value of 10,000 by the present system.

The present understanding and modes of explanation of the phenomena which present themselves in such an arrangement is such that any theory of operation which may be advanced in regard to them is merelyan at tempt to explain the results attained in language which will be understandable to Athose skilled in the art and I desire it to be understood that this invention is not to be -lim-v ited by any statement of theory advanced herein, but is to be construed in the-light of the results attained. The circuit shown in Fig. 2 is similar' to that shown in Fig. 1, with the exception that the grid leal: 24 is shunted around the condenser 7 and the condenser 15 is omit-ted, the variation in impedance of the circuit be-l ing produced by the inductance 14 alone. In this figure the inductance 14 is shown as being provided with an iron core, but this is not essential, in fact, I believe the air core inductance to be productive of the better The circuit shown in F ig.. 3 is substantial`' ly the sameas that shown in Fig. 2, with thevexception that vthe inductance 14 is coupled to t-he secondary 4 of the oscillation transformer. lVith the interrupter rotating and a signal being received, the interrupter opens and closes the circuit of the inductance `-1'4, thereby rapidly varying the electrical time. constants of thel grid circuit, and changing it from an oscillating condition to anoir-oscillating condition. lVith the in, terrupter closed, the incoming signal 'will produce oscillations in the grid circuit, which are`built up by the feed back inductance 22. I'Vhen the'interrupter opens the oscillations immediately and abruptly cease, causing a distinct signal in the telephones;

In the arrangement shown in Fig. 4, am-

plication of the received signal is accomplished by rapidly varying the coupling between the feed back'inductance 22 and the secondary of the 'oscillation transformer, preferably by rotating the induetance at a high angular' velocity. When the axes of the inductan'ces 4"and 22 are in alinement, the current in the grid circuit is amplified and when the inductances are at right angles, no' amplification occurs.v

In the arrangement shown in Fig. 5, the controlling inductance 14' is shunted by a revolving condenser 25,. the function of Which is to vary the capacitybetween maximum and minimum values at a high rate. The value of the inductance is such that 4when the capacitance is a minimum, the circuit does not oscillate and when the Acapacitance is a maximum, the incoming oscillations are amplified to produce oscillations in the circuit. `The circuitis thus rapidly converted from an oscillating condition to a non-oscillating condition and vice versa, atl a frequency Within the range of audiu1 ity.

In Fig. l6 I have shown a modified forni of circuit, in which the feed back circuit is` omitted. The secondary 4 ofthe oscillation transformer is connected to 'the ,grid of a thermo-ionic vacuum tube 26, which serves las an amplifier. The plate circuit of the amphtier'tube contains theprimary 27 of thev oscillatien 'transformer .28 and the battery 29, 'and amplified oscillations are produced in ythe plate circuit.,` The secondary 31 of the oscillation transformer 28 is connected tothe grid of the ,thermo-ionic vacuum ktube 32, the plate circuit of Which tube contains the telephones 33 and the common batter 29.

'The grid circuit is provided, as in Flg. 1,

with an inductance 34 which is shunted out of and into the grid circuit by the rotating interrupter or commutator 35.

I claim:

."A radio 'receiving system, including a thermo-ionic vacuum tube, a grid circuit, a plate lcircuit inductively coupled with the grid circuitsai d grid circuit being normally non-oscillatory, an inductance in the said grid circuit,.the impedance of which is sufiiciently high to stop the` flow of current in the grid circuit and an interrupter shunting said inductanee.

In testimony whereof, I have hereunto set my hand.

CHARLES v. LoGWooD. 

